Go language -init() function - package initialization

init Similarities and differences between function and main function

• init() main() All are go Reserved functions in language . from go Program calls automatically , Cannot be called manually .
• init() The definition of the function is similar to that of the main function , Parameters cannot have and return values .init() The function executes before the main function executes .
• init() Functions can be defined in any package , And multiple... Can be defined repeatedly . The main function can only be used in main It's a bag , And only one .
• One package Can be imported multiple times by other packages , But initialization can only be performed once .

We can define it in the code init() function . This function will execute when the package is imported .

for example . If it's true main Import package from , There is... In the package init() function , that init() The code in will be in main() Execute before function execution , Used to initialize the specific data required by the package .

init() Function execution order

• In the same package ,init() Function from top to bottom .
• In the same package Different go In file ,init() The function is based on go Sort the string of file name .
• Different package in , If we don't depend on each other , according to import Sequential execution init() function .
• If package There is dependence ,init() The order of function calls is ： The last package to be relied on , The first to perform .